Space Manipulator Control For The Dymaflex Flight Experiment

Unlike traditional xed-base manipulators, manipulators used in space are mounted to a spacecraft which

may move freely in response to any forces or torques. This results in a highly coupled dynamical system.

In the past, robotic arms have often been slow and lightweight in comparison to their host spacecraft;

but as economic incentives drive the development of smaller, faster, lighter vehicles, this coupling will

present an increasing challenge in the development of suitable control systems. To improve understanding

of the dynamics of this coupled system and to demonstrate and validate proposed controllers in the space

environment, the University of Maryland Space Systems Lab is constructing the DYnamic MAnipulation

FLight EXperiment (DYMAFLEX) microsatellite, the development of which is partially funded by the

United States Air Force University Nanosat Program. Equipped with a high-performance manipulator

representing approximately 14% of the mass of the combined system and having greater rotational inertia

at full extension than the spacecraft itself, the DYMAFLEX vehicle represents the ideal test bed for space

manipulator dynamics and control. This paper presents an overview of space manipulator control as it relates

to the DYMAFLEX science mission, with simulation results exploring an intended maneuver in Cartesian

space. The mission is designed to provide empirical validation of existing models for the behavior of a

space manipulator as well as to provide a basis for comparison between proposed control strategies to assess

their strengths and weaknesses in the actual application environment. In this paper, a simple Transpose

Jacobian controller is compared to more sophisticated approaches, including the Modied Transpose Jacobian

controller of Papadopoulos and Moosavian. A technique is proposed for mitigating the chattering problem

associated with the MTJ strategy. The eect of measurement noise is explored. An adaptive controller is

considered as a further means of improving performance. Preliminary conclusions are drawn, to be veried

on the DYMAFLEX platform.